There are as yet no precise and practical methods to assess the kidney's ability to recover from changes induced by chronic hydroureteronephrosis (HUN) or prolonged hypothermic storage before transplantation. We therefore propose to test the sensitivity of in vivo phosphorus-31 magnetic resonance spectroscopy (31P-MRS) as an indicator of renal tissue damage and to establish a method of distinguishing reversible from irreversible changes. Our specific aims are: 1. To assess, in the porcine model, in situ renal tissue damage from various insults of obstructive HUN, including (a) acute complete obstruction (n = 10); (b) chronic complete obstruction (n = 10); and (c) chronic partial obstruction (n = 10). The 31P-MRS assessment will be complemented by magnetic resonance imaging (MRI) and nuclear scintigraphy. 2. To develop the use of 31P-MRS in cold-stored canine (n = 15) and human (n = 20) kidneys as an indicator of renal transplant viability. The effects of ischemia will be examined. Histologic, MRI, and nuclear scintigraphic examination will augment MRS. 3. To monitor the bioenergetic state of transplanted canine kidneys in situ by 31P-MRS. Initial studies will be performed with MRS detection coils surgically implanted around the in situ kidney. After assessment of various signal localization procedures, subsequent experiments will be performed with detection coils placed on the dog's exterior. Measurements of glomerular filtration rates and effective renal plasma flow rates by nuclear scintigraphy will be correlated with the MRS and MRI observations. The results of this study will: help determine whether the 31P-MRS parameters of renal transplant viability are valid for human cadaveric kidneys; enable application of these parameters in clinical situations; and assess renal viability in chronic obstruction and the transplantation setting.